The tilde or ~; also referred to informally as squiggly or squiggle(s)) is a grapheme with several uses. The name of the character comes from Portuguese and Spanish, from the Latin titulus meaning "title" or "superscription", though the term "tilde" has evolved and now has a different meaning in linguistics. Some may refer to it as a "flourish". It was originally written over a letter as a scribal abbreviation, as a "mark of suspension", shown as a straight line when used with capitals. Thus the commonly used words Anno Domini were frequently abbreviated to Ao Dñi an elevated terminal with a suspension mark placed above the "n". Such mark could denote the omission of one letter or several letters. This saved on the expense of the scribe's labour and the cost of vellum and ink. Mediaeval European charters written in Latin are largely made up of such abbreviated words with suspension marks; only uncommon words given in full. It has since acquired a number of other uses as a diacritic mark or a character in its own right. These are encoded in Unicode at U+0303 ◌̃ combining tilde and U+007E ~ tilde (as a spacing character), and there are additional similar characters for different roles. In lexicography, the latter kind of tilde and the swung dash (⁓) are used in dictionaries to indicate the omission of the entry word.[1] This symbol (in English) informally[2] means "approximately", such as: "~30 minutes ago" meaning "approximately 30 minutes ago".[3] It can mean "similar to",[4] including "of the same order of magnitude as",[2] such as: "x ~ y" meaning that x and y are of the same order of magnitude. Another approximation symbol is ≈, meaning "approximately equal to"[3][4][5] the critical difference being the subjective level of accuracy: ≈ indicates a value which can be considered functionally equivalent for a calculation within an acceptable degree of error, whereas ~ is usually used to indicate a larger, possibly significant, degree of error. The tilde is also used to indicate equal to, or approximately equal to by placing it over the "=" symbol. In some languages, the tilde is used as a diacritical mark ( ˜ ) placed over a letter to indicate a change in pronunciation, such as nasalization. It was first used in the polytonic orthography of Ancient Greek, as a variant of the circumflex, representing a rise in pitch followed by a return to standard pitch. Later, it was used to make abbreviations in medieval Latin documents. When an 〈n〉 or 〈m〉 followed a vowel, it was often omitted, and a tilde (i.e., a small 〈n〉) was placed over the preceding vowel to indicate the missing letter; this is the origin of the use of tilde to indicate nasalization (compare the development of the umlaut as an abbreviation of 〈e〉.) The practice of using the tilde over a vowel to indicate omission of an 〈n〉 or 〈m〉 continued in printed books in French as a means of reducing text length until the 17th century. It was also used in Portuguese, Catalan and Spanish. The tilde was also used occasionally to make other abbreviations, such as over the letter 〈q〉 ("q̃") to signify the word que ("that"). It is also as a small 〈n〉 that the tilde originated when written above other letters, marking a Latin 〈n〉 which had been elided in old Galician-Portuguese. In modern Portuguese it indicates nasalization of the base vowel: mão "hand", from Lat. manu-; razões "reasons", from Lat. rationes. This usage has been adopted in the orthographies of several native languages of South America, such as Guarani and Nheengatu, as well as in the International Phonetic Alphabet (IPA) and many other phonetic alphabets. For example, [ljɔ̃] is the IPA transcription of the pronunciation of the French place-name Lyon. In Breton, the symbol 〈ñ〉 after a vowel means that the letter 〈n〉 serves only to give the vowel a nasalised pronunciation, without being itself pronounced, as it normally is. For example 〈an〉 gives the pronunciation [ãn] whereas 〈añ〉 gives [ã]. The tilded 〈n〉 (〈ñ〉, 〈Ñ〉) developed from the digraph 〈nn〉 in Spanish. In this language, 〈ñ〉 is considered a separate letter called eñe (IPA: [ˈeɲe]), rather than a letter-diacritic combination; it is placed in Spanish dictionaries between the letters 〈n〉 and 〈o〉. In addition, the word tilde can refer to any diacritic in this language; for example, the acute accent in José is also called a tilde in Spanish.[6] Current languages in which the tilded 〈n〉 (〈ñ〉) is used for the palatal nasal consonant /ɲ/ include: In Vietnamese, a tilde over a vowel represents a creaky rising tone (ngã). In phonetics, a tilde is used as a diacritic either placed above a letter, below it or superimposed onto the middle of it (see International Phonetic Alphabet → Diacritics): A tilde above a letter indicates nasalization, e.g. [ã], [ṽ]. A tilde superimposed onto the middle of a letter indicates velarization or pharyngealization, e.g. [ɫ], [z̴]. If no precomposed unicode character exists, the unicode character U+0334 ◌̴ combining tilde overlay can be used to generate one. A tilde below a letter indicates laryngealisation, e.g. [d̰]. If no precomposed unicode character exists, the unicode character U+0330 ◌̰ combining tilde below can be used to generate one. In Estonian, the symbol 〈õ〉 stands for the close-mid back unrounded vowel, and it is considered an independent letter. Some languages and alphabets use the tilde for other purposes: Some languages and alphabets use the tilde for other purposes: Arabic script: A symbol resembling the tilde (maddah U+0653 ـٓ arabic maddah above) is used over the letter 〈ا〉 (/a/) to become 〈آ〉, denoting a long /aː/ sound ([ʔæː]). Guaraní: The tilded 〈G̃〉 (note that 〈G/g〉 with tilde is not available as a precomposed glyph in Unicode) stands for the velar nasal consonant. Also, the tilded 〈y〉 (〈Ỹ〉) stands for the nasalized upper central rounded vowel [ɨ̃]. A small number of other alphabets also use 〈g̃〉. Unicode has a combining vertical tilde character, ̾ (U+033E). It is used to indicate middle tone in linguistic transcription of certain dialects of the Lithuanian language[7] and for transliteration of the Cyrillic palatalization sign, ҄ (U+0484).[citation needed] Most modern proportional fonts align plain spacing tilde at the same level as dashes, or only slightly upper. This distinguish it from small tilde ˜, which is always raised. But in some monospace fonts, especially used in text user interfaces, ASCII tilde character is raised too. This apparently is a legacy of typewriters, where pairs of similar spacing and combining characters relied on one glyph. Even in line printers' age character repertoires were often not large enough to distinguish between plain tilde, small tilde and combining tilde. Overprinting of a letter by the tilde was a working method of combining a letter. The swung dash (~) is used in various ways in punctuation: In some languages (though not English), a tilde-like wavy dash may be used as punctuation (instead of an unspaced hyphen or en-dash) between two numbers, to indicate a range rather than subtraction or a hyphenated number (such as a part number or model number). Before a number the tilde is used to mean "approximately"; "~42" means "approximately 42".[8] Japanese and other East Asian languages almost always use this convention, but it is often done for clarity in some other languages as well. Chinese uses the wavy dash and full-width em dash interchangeably for this purpose. In English, the tilde is often used to express ranges and model numbers in electronics but rarely in formal grammar or type-set documents, as a wavy dash preceding a number sometimes represents an approximation (see the Mathematics section, below). The wave dash is used for various purposes in Japanese, including to denote ranges of numbers, in place of dashes or brackets, and to indicate origin. The wave dash is also used to separate a title and a subtitle in the same line, as a colon is used in English. When used in conversations via email or instant messenger it may be used as a sarcasm mark. The sign is used as a replacement for the chouon, katakana character, in Japanese, extending the final syllable. In informal messaging in China the tilde is sometimes used at the end of sentences to indicate a semi-excited but not alarmed tone; somewhere between a "." and a "!".[9][citation needed] In mathematics, the tilde operator (Unicode U+223C), sometimes called "twiddle", is often used to denote an equivalence relation between two objects. Thus "x ~ y" means "x is equivalent to y". It is a weaker statement than stating that x equals y. The expression "x ~ y" is sometimes read aloud as "x twiddles y", perhaps as an analogue to the verbal expression of "x = y".[16] The tilde can indicate approximate equality in a variety of ways. It can be used to denote the asymptotic equality of two functions. For example, f (x) ~ g(x) means that limx → ∞ f( x) ∕ g(x) = 1.[2] A tilde is also used to indicate "approximately equal to" (e.g. 1.902 ~= 2). This usage probably developed as a typed alternative to the libra symbol used for the same purpose in written mathematics, which is an equal sign with the upper bar replaced by a bar with an upward hump, bump, or loop in the middle (♎) or, sometimes, a tilde (≃). The symbol "≈" is also used for this purpose.